It is random to an extent but not entirely, read what the quote says, they will need specific profiles or at least a range that they will want to test out, if there are 1232133243 people in that range, then probably random, if only 2 people, then those 2 will probably get in.

---------- Post added 2012-02-24 at 07:39 AM ----------

Holy crap just saw this news:

This was posted on Reddit tonight
Hey guys, you’ve probably seen that we’re taking sign-ups for a chance to be in the GW2 beta. https://beta.guildwars2.com/
One of the things we need to test is World vs. World, a massive PvP format where hundreds of players fight each other in three-way battles against other shards.

We need tens of thousands of people to test this!

One of our WvW designers, Mike Ferguson, is going to be on reddit TOMORROW morning at 8:00 AM PST to answer your questions about World vs. World.
Like we did for our last AMA with the ArenaNet designers, Mike will be posting on this account http://www.reddit.com/user/ArenaNetTeam/

We’d love to see you all there with all your burning questions about WvW and it would be awesome to make sure the reddit gaming community knows about this so they can ask questions, too.

"Bill Nye: So Todd I got an offer for you. You and me. Any time. Any place. Debating science mano- a-mano. I'll bring the facts, and you bring the Vaseline. Because your ass is gonna fucking need it when I'm done whipping."

They'll need a diverse selection of systems in all ranges, from the lowest end toaster ovens, to the nuclear-powered ultramachines. They'll need people with CPUs both Intel and AMD, they'll need laptops, they'll need graphics cards of all shapes and sizes.

from the lowest end toaster ovens, to the nuclear-powered ultramachines

lowest end toaster ovens

toaster

Huzzah, I'm guaranteed a spot!

Me, I hope I can contribute by testing the stability of an overclocked Bulldozer AMD CPU along with a Crossfire-setup AMD (obviously) GPU.